I've wondered about this, too. Conventional wisdom says don't do strength training for the same muscle group 2 days in a row ever EVER or your bottom will explode or something.

But CW says a lot of stuff that's not true for everyone and I'm generally in favor of ignoring it in favor of what works for you. (E.g., eating small meals every 4 hours does NOT work for me.)
So for me, I guess I'll not worry too much about the body weight squats I do during breaks at work vis a vis when I work legs heavy at the gym.